A magnetic encoder device has a configuration in which a multipolar magnet opposed to a magnetic sensor is rotated to detect passage of each of magnetic poles N and S of the multipolar magnet by the magnetic sensor, to thereby detect rotation of a rotary member. As this type of magnetic encoder device, there is publicly known the one that is incorporated into a bearing device for a wheel of an automobile and is used to detect the number of rotations of the wheel for an antilock brake system (ABS), as disclosed in, for example, JP 2010-249536 A (Patent Literature 1). In the magnetic encoder device, the multipolar magnet opposed to the magnetic sensor is formed by injection molding of a magnet material containing a magnetic powder and a thermoplastic resin.
On the other hand, as disclosed in, for example, JP 2009-80058 A (Patent Literature 2), there is known, as the magnetic encoder device, the one in which magnetic encoder tracks are arranged in a double row so that an absolute angle (rotation phase) of a rotary shaft can be detected based on a phase difference between magnetic signals detected in different tracks.